Some T cells recognize lipid antigens presented by class I MHC-like CD1 molecules. Although self-lipid antigens activating them have not yet been identified, most NK T cells are thought to be autoreactive and can be rapidly activated by a surrogate glycolipid ligand alpha-galactosyl ceramide or alpha-GalCer. To characterize self-glycolipid-reactive T cells, their phenotype and their physiological function, we have focused on the recognition of a major myelin-derived glycolipid, sulfatide, (3'-sulfated beta-galactosyl ceramide). We have generated sulfatide-CD1d-tetramers and have identified sulfatide-reactive T cell populations in the liver, thymus and spleen from naive C57BL/6 mice. We have also generated sulfatide-reactive T cell hybridomas. During the course of antigen-induced experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis (MS) in humans, sulfatide-CD1d-tetramer+ T cells are selectively increased several-fold within the central nervous system. Treatment with sulfatide can both prevent and reverse ongoing EAE in wild type but not in CD1d-deficient mice. Based on our findings we propose that sulfatide is a self-glycolipid ligand recognized by a distinct population of CD1d-restricted T cells that can be activated to modulate autoimmune responses. We will use sulfatide- and a-GalCer-CD1d-tetramers and antibodies against various cell surface markers on NK T cells to characterize the phenotype of sulfatide-reactive T cells. Sulfatide-reactive T cell hybridomas will be used to analyze the antigen fine specificity and the TCR V-gene repertoire. Using glycolipid tetramers and Elispot analysis we will determine the dynamics of their activation and investigate mutual interactions among different lipid-reactive T cell populations. We will determine the number, phenotype and the fate of NK cells, B cells and myelin protein-reactive pathogenic CD4 T cells following sulfatide injection of wild type and CD1d-deficient mice. In adoptive transfer experiments we will directly examine the regulatory potential of sulfatide-CD ld-tetramer+ T cells. Neutralizing antibodies and mice genetically deficient for type 1 and 2 cytokines will be used to determine their role in the modulation of EAE by sulfatide. We will optimize treatment of ongoing disease with sulfatide in order to explore its therapeutic potential. These studies are important not only for understanding the biology of a naturally occurring self-glycolipid-reactive T cell population, but also because of the highly conserved nature of CD1d molecules across species they will form the basis for manipulation of human autoimmune demyelinating diseases, such as MS.